Wireless networks have become ubiquitous. A wireless network refers to any type of computer network that is wireless, and is commonly associated with a telecommunications network whose interconnections between nodes is implemented without the use of wires. Wireless telecommunications networks are generally implemented with some type of remote information transmission system that uses electromagnetic waves, such as radio waves, for the carrier and this implementation usually takes place at the physical level or layer of the network.
A wireless network consists of several components. These are WCs (Wireless Controllers), WSs (Wireless Switches), APs (Access Points) and MUs (Mobile Units). An MU is a mobile wireless device like a laptop or a VOIP phone set that communicates with other wired or wireless devices over a wireless network. A wireless AP is a device that allows wireless communication devices (MUs) to connect to wireless and wired networks. A WS receives and switches data traffic sent from several MUs via several APs to the enterprise network
A WC handles provisioning, configuration, authentication, load balancing and monitoring of WSs, APs and MUs. The WSs, APs and MUs establish secure control channels to WCs for this purpose and exchange control traffic with it. The Wireless Controllers authenticate WSs, APs, MUs and control the coordination between them to provide a seamless mobile network to the end users. In some cases, the WC and WS functions may be integrated in one device. In such cases, the term MS (Mobility Switch) will be used.
The AP acts as a bridge between the MUs on the wireless side and WSs/WCs present on the wired side. The AP performs authentication, authorization, accounting and load balancing of MUs by communicating with the WC. After obtaining authorization by WC, the AP tunnels MU data traffic into the WS assigned by WC for switching.
A WS switches data traffic originated by MUs into both wired and wireless networks. The wireless switches allow mobile units (e.g. MUs like laptops, cell phones etc.) to roam among various locations and still have network access.
A typical wireless network may include a Mobility Domain (MD). The MD includes one or more Access Points (APs), one or more Wireless Switches (WSs), one or more Wireless Controllers (WCs) and one or more Mobile Units (MUs) and is centrally managed for provisioning, configuration and monitoring. A mobility domain is typically a single geographic area where a same set of mobility services is provided. A mobility domain can include tens of WCs, hundreds of WSs, thousands of APs, and tens of thousands of MUs. MUs can include laptops, cell phones, Personal Digital Assistants (PDAs) and the like.
MUs (like Laptops, VOIP phones etc) associate with an AP, get authenticated and become a part of MD. As they physically roam, they disconnect from one AP in the MD and get attached to another AP in the MD.
Since an AP or a WS sends control traffic to the WC to which it is associated, associating a large number of these entities to a single WC will heavily load the processing power of the WC. Hence when an AP or WS boots up, it contacts a predetermined WC which load balances and distributes these entities to all the WCs in the MD.
Similarly there is need for distributing wireless data traffic from APs (originated by MUs attached to the APs) evenly across the WSs so that no WS is burdened too heavily. This distribution function is also done by the WC that performs the load balancing. Traditionally the APs have been load balanced and assigned to WCs either by way of manual configuration or by using a “round robin” or “least loaded WC” methods without using location information. In cases where WC and WS are deployed as separate devices, there is also need to load balance control channel traffic of both APs and WSs to WCs. In all cases, one designated WC does the load balancing of WSs/APs to WCs, and load balancing of APs to WSs.
In a large enterprise, when WLAN controllers bootup during initial deployment or when they boot up after a power failure, the APs get assigned to controllers that come up early and the AP load distribution across them can be suboptimal. Similarly, when new controllers are added to the enterprise, they will have no load unless some APs are assigned to the new controllers. In such a case, the user may have to intervene and manually reassign APs to controllers to balance the load.